Abstract The capacity of the ventricles to perform work (i.e., generate power) is essential for moving blood throughout the circulatory systems. Ventricular power is determined by the power generating capacity of the myofilaments within the cardiac myocyte. However, the sub-cellular processes that regulate myofilament power are incompletely understood. The overall objective of this proposal is to use biochemical, biophysical, and transgenic tools to discern (i) thin filament and (ii) thick filament-based mechanisms that regulate power and (iii) integrate these control mechanisms into a computational model that can predict how sarcomere-level modifications impact hemodynamics. The two mechanistic hypotheses are (Aim 1) alterations in the functional rigidity of thin filament regulatory units modulate cooperative recruitment of cross-bridges, which, in turn, determines power and (Aim 2) phosphorylation of myosin binding protein- C (MyBP-C) per se increases myofibrillar power output by three distinct biophysical mechanisms. In (Aim 3), a multi-state kinetic model of sarcomeric power output will be generated whereby thin and thick filament dynamic properties can be manipulated and evaluated for functional impacts to cooperativity and power. Aim 3 goes beyond the sarcomere and uses multiscale modeling to predict how strategic manipulation of myofilament targets will impact ventricular function and hemodynamics, which will be experimentally tested in a hypothesis-driven manner. Multi-scale modeling will provide a new platform to interrogate biophysical modifications that produce the largest functional effects and, thus, illuminate high-value therapeutic targets to optimize ventricular performance in patients with genetic and adaptive cardiomyopathies.